// compute n!

#include <iostream>

using namespace std;

int factorial(int n)
{
    if(n <= 1)
        return 1;
    else
        return n * factorial(n -1);
}

int main()
{
    cout << "0! = " << factorial(0) << endl;
    cout << "1! = " << factorial(1) << endl;
    cout << "5! = " << factorial(5) << endl;
    return 0;
}